Wave-front aberrations analysis by Zernike polynomials based on the annular sub-aperture stitching system

Characterisation of a large aperture steep concave parabolic mirror using SASI based on auto-collimation theory

“…Auto-collimation [7,8] and sub-aperture stitching [9][10][11][12][13][14][15][16][17][18] are two major interferometry methods used for parabolic mirrors. When a concave parabolic mirror is under test, its focal point should be suitable with a standard lens for auto-collimation; if the relative aperture of the parabolic mirror is larger than the standard lens, then the surface of the entire aperture could not be obtained.…”

“…In addition, auto-collimation requires the same aperture standard flat mirror as the parabolic mirror under test; however, the requirement of a large aperture and high precision accuracy flat mirror makes it difficult to realise. Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer; however, when the deviation of a parabolic mirror becomes larger, its corresponding interferograms will be thicker for not only the annular sub-aperture stitching method [9,10] but also for the circular sub-aperture stitching method [11][12][13][14][15][16][17][18], and the corresponding interferogram processing will become more difficult. In addition, sub-aperture stitching requires a precision platform with six degrees of freedom to implement the complex adjustment of the parabolic mirror under test.…”